We report on the magnetic and structural properties of two
types of nanostructures doped with Co or Mn, namely, ZnO
nanowires and colloidal ZnO nanocrystals. Electron paramagnetic
resonance (EPR) spectra have been measured and
analysed to extract information on the incorporation of the
ions in the lattice. A detailed analysis by means of simulations
of the experimental EPR spectra confirms that the transition
metal (TM) ions were mainly incorporated as TM2+,
occupying the Zn2+ sites in the wurtzite structure of ZnO. Furthermore,
for both types of nanostructures, the EPR spectra
are composed of more than one signal, revealing locally distorted
environments or core-shell structures, proved by surface
modifications via inorganic coatings.